We demonstrate applying synchrotron radiation based high resolution X-ray photoelectron spectroscopy as a versatile in-situ tool to study the step-wise formation and nitridation of indium gallium (InGa) composite droplets on Si(1 1 1) 7 x 7. This includes analysis of initial interactions of Ga and In with Si(1 1 1)7x7, and characterization of formation and nitridation of InGa droplets. The results show that after stabilization of Si(1 1 1) 7 x 7 structure with Ga and In at 750 degrees C and formation of Ga nanodroplets as the bases, the InGa composite droplets (In:Ga approximate to 3:1) were formed at RT and 200 degrees C in a coverage range 3-14 monolayers. The nitridation efficiency and structure of the droplets/Si(1 1 1) with NH3 were temperature dependent. At or below 350 degrees C, the droplets were hardly nitridated. At 670 degrees C, the nitridation of InGa was more completed, which however caused an unavoidable nitridation of Si surface. The optimum nitridation occurred around 480 degrees C and proceed in a 2D mode. Further simultaneous growth and nitridation of the InGa droplets on the 2D nitridated surface at 400 degrees C resulted in a complex surface composition and structure. An ex-situ atomic force microscopy reveals both the aligned metallic droplet-island assemblies and the fractured nitridated island bases with small droplets on top for the final surface. (C) 2014 Elsevier B. V. All rights reserved.